I typically just grab the text in the 'answer' , move it to the original question, then replace the answer with something like this:
Your additional information has been
automatically added as an addendum to
your original question. Note,
automatically does not infer a system
process, Jeff Atwood has me captive in
a warehouse with an automatic weapon
pointed at me, hence the term.
If you continue to post updates to
your question as answers, he might
pull the trigger. Please help me live.
I am of course kidding. But the text is similar. Mostly, new users just 'get it' and delete the now edited 'answer'.